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Selection Criteria for Particulate Filters
filters certified under NIOSH's current Part 84 requirements are
generally acceptable for negative pressure respiratory protection
against all aerosols, mists, fumes, and dusts subject to the filter
stated limitations. These filters will be labeled with a letter N,
R or P and a number representing the efficiency, 95, 99 or 100.
An exception for usability occurs when a substance specific OSHA standard, e.g. lead,
requires a specific filter efficiency. If one of these standards requires a High
Efficiency Particulate Air (HEPA) filter to comply with its requirement, the user should
select a filter with a labeled efficiency number of 100.